1. Field of Invention
The present invention relates to a photovoltachromic device. More particularly, the present invention relates to a photovoltachromic device with fast response times.
2. Description of Related Art
The concept of electrochromism was presented in 1961, i.e. an electrochromic material will change its color when a voltage is applied thereto. For example, when being illuminated with visible light, an electrochromic device will block the light of specific wavelengths from passing therethrough, thereby preventing excess light from passing through the electrochromic device and adjusting quantities of incident light of different wavelengths.
An electrochromic layer may be enabled using an organic compound, such as viologen or pyrodine, or inorganic compound, such as inorganic transition metal compounds WO3, MoO3 and V2O5. According to various optical properties of an electrochromic device, the electrochromic device can be applied on smart windows for adjusting the quantity of incident sunlight, automobile anti-dazzling rear view mirrors, automobile sunroofs, static display devices or digital displays, etc.
Referring to FIG. 1, FIG. 1 is a schematic cross-sectional view illustrating a conventional photovoltachromic device 100. The photovoltachromic device 100 includes a first transparent electrode 110, a first transparent substrate 112, a second transparent electrode 120, a second transparent substrate 122, an electron-transport layer 130, an electrochromic layer 140 and an electrolyte layer 150. The first transparent substrate 112 is used to support the first transparent electrode 110. The second transparent substrate 122 is used to support the second transparent electrode 120. The second transparent electrode 120 is electrically connected to the first transparent electrode and disposed facing the first transparent electrode 110. The electron-transport layer 130 is disposed on a surface facing the second transparent electrode 120 of the first transparent electrode 110, and the electron-transport layer 130 has a sensitizing layer 132 adsorbed thereon. The electrochromic layer 140 covers the second transparent electrode 120 entirely, thereby totally separating the second transparent electrode 120 from the electrolyte layer 150, i.e., there is no surface area of the second transparent electrode 120 contacting the electrolyte layer 150. The electrolyte layer 150 includes a redox pair and is disposed between the first transparent electrode 110 and the second transparent electrode 120.
Light illumination can excite the sensitizing layer 132 to generate photoelectrons, such that the electrochromic layer 140 is colored by generating a potential difference, thereby enabling the electrochromic layer 140 to achieve desired optical features.
Under the conditions of external circuit shorted or no light illumination, the electrochromic layer will bleach gradually but very slowly. Hence, the photovoltachromic device has the disadvantages of poor light response time and inconvenient operation. Further, the conventional photovoltachromic device 100 does not have obvious photovoltaic characteristics and thus cannot be finely tuned for coloring.